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S.I. Chen, C. Hou, W.V. Good, A. Chandna, A.M. Norcia, M.W. Pettet; Early–Stage versus Late–Stage Amblyopia: Results From the VEP Vernier Paradigm . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4308.
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Vernier and Snellen acuity measures are well correlated in adults with amblyopia but there is little evidence of whether this is also true in children with untreated amblyopia.
Using sweep VEP measures, we compared the monocular amplitude versus vernier displacement functions of a group of adults with amblyopia (n = 39, 17 anisometropes, 22 strabismics) and a group of equally amblyopic but previously untreated children (n= 21, 10 anisometropes, 11 strabismics). A group of normal adults (n= 37) and normal children (n = 16) acted as controls. Both the normal children and the children with amblyopia were tested again, the amblyopes at the end of treatment. Vernier offset was swept from 0.5 to 8 arcmin using at 3.75 Hz vernier onset/offset stimulus.
Suprathreshold amplitude reductions in the amblyopic eye were greater in children than in adults with anisometropic amblyopia and were substantial in both. In contrast there was little effect of amblyopia in strabismic children, while a substantial one was observed in adults. The suprathreshold response of the dominant eye of untreated anisometropes is super–normal relative to age–matched controls. Amblyopia treatment reduced the amplitude of the response function in the dominant and increased its amplitude in the non–dominant eye of anisometropic children. Little change was seen in response functions of either eye of children with strabismic amblyopia despite documented improvement in optotype measures.
The pattern of vernier losses are similar between strabismic and anisometropic amblyopia in its late–stage in adults, but not the early stages of the disease. These findings further suggest a fundamental difference between the pathogenesis of vernier–related losses in anisometropic versus strabismic amblyopia.
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